Tapered stress joint configuration

A stress joint comprising:

• a termination riser joint adapted for connecting to a lower end of a riser;
• an upper transition section extending below and having an upper end joined to a lower end of the termination riser joint, the upper transition section tapering from a larger outer diameter at the upper end of the upper transition section to a smaller outer diameter at a lower end of the upper transition section;
• an intermediate section below the upper transition section and having an outer diameter that is the same as the smaller outer diameter of the upper transition section;
• a lower transition section below the intermediate section and tapering from the outer diameter of the intermediate section to a lower outer diameter larger than the outer diameter of the upper end of the upper transition section;
• and
• a flange at a lower end of the lower transition section for connecting the stress joint to subsea equipment.

A subsea production riser for connecting a surface structure to subsea equipment, the riser comprising:

• a string of production riser sections extending from an upper end near the surface structure to a lower end near the subsea equipment, the riser sections having an outer diameter;
• and
• a riser stress joint between the lower end of the string of production riser sections and the subsea equipment, the riser stress joint having an upper riser transition section gradually reducing in outer diameter in a downward direction and joining a cylindrical intermediate riser section that has a constant outer diameter less than the outer diameter of the riser sections and a lower riser transition section that joins the intermediate riser section and extends downward, the lower riser transition section increasing in outer diameter in a downward direction;
• and
• the upper riser transition section having a length less than the lower riser transition section and less than the intermediate riser section, the intermediate riser section having a length less than the lower riser transition section.

A subsea riser for connecting a surface structure to subsea equipment,

• the riser comprising:
• a string of riser sections extending from an upper end near the surface structure to a lower end near the subsea equipment, the riser sections having an outer diameter;
• a riser stress joint between the lower end of the riser string and the subsea equipment, the riser stress joint comprising:
• a termination riser joint connected to a lower end of the riser string;
• an upper transition section welded to a lower end of the termination riser joint and tapering from a larger wall thickness at an upper end of the upper transition section to a smaller wall thickness at a lower end of the upper transition section;
• an intermediate section below the upper transition section, the intermediate section having a wall thickness that is the same as the smaller wall thickness of the upper transition section;
• a lower transition section below the intermediate section and tapering from the wall thickness of the intermediate section to a lower wall thickness larger than the wall thickness of the upper end of the upper transition section;
• the upper transition section, intermediate section, and lower transition section having inner surfaces that form a uniform diameter cylindrical passage inside the riser stress joint;
• an axial dimension of the upper transition section measured along an axis of the stress joint being less than an axial dimension of the intermediate section;
• and wherein
• axial forces in the riser pass through the termination riser joint, upper transition section, intermediate section and lower transition section to the subsea equipment.